A view of the Merck & Co. campus in Linden, New Jersey March 9, 2009. REUTERS/Jeff Zelevansky

Sales of Januvia and a related drug called Janumet, the company’s biggest franchise, fell 12 percent to $1.45 billion. Merck said wholesalers had stocked up in the prior quarter, and the products face growing competition from other oral diabetes treatments.

But Adam Schechter, the company’s head of global human health, said Januvia sales should increase this year, excluding the effects of a stronger dollar, which reduces the value of revenue from overseas.

Sales of Remicade, which is facing competition outside the United States from cheaper biosimilars, dropped 29 percent to $396 million. In a conference call with analysts, Schechter said the drug’s market share was shrinking, and the trend would accelerate.

Merck is counting on Keytruda, a recently approved treatment for melanoma and lung cancer, to boost its earnings for years to come. The medicine, which takes the brakes off the immune system, is competing with Bristol-Myers Squibb Co’s (BMY.N) similar Opdivo treatment, which is picking up sales faster.

Keytruda sales rose to $214 million in the fourth quarter, about half Opdivo’s $475 million in revenue in that period.

Merck, the second-largest U.S. drugmaker behind Pfizer Inc (PFE.N), forecast full-year earnings of $3.60 to $3.75 per share, excluding special items. The analysts’ average estimate was $3.72, according to Thomson Reuters I/B/E/S.

Fourth-quarter revenue fell 3 percent to $10.22 billion, below analysts’ expectations of $10.35 billion. Sales would have risen 4 percent if not for the stronger dollar.

Net income fell to $976 million from $7.32 billion.

Excluding costs from last year’s acquisition of Cubist Pharmaceuticals and other special items, earnings of 93 cents per share topped Wall Street’s forecast of 91 cents. Analysts largely attributed the profit beat to a lower tax rate.